The use of electrosurgical energy in vessel sealing surgical procedures is common and has been used in conjunction with a variety of surgical techniques for many years. In general, electrosurgical devices used in vessel sealing rely on a combination of pressure and high frequency electric energy applied to biological tissue as a way to cut, coagulate, desiccate or seal tissue, for example, blood vessels. In the case of vessel sealing, the electrosurgical energy acts to create collagen melting and tissue fusion. Most RF surgical devices on the market today and described in the prior art have power delivery systems and end effectors that are sized to accommodate a wide range of situations, tissue thicknesses, tissue volume, and end effector bite sizes. In particular, vessel sealing technology has always relied upon the use of relatively high current settings and large end effector sizes to create a seal in varying surgical situations. No one has been able to produce a reliable vessel sealing instrument that operates at currents below 2 Amps.
For coagulation or blood vessel sealing with known devices, the average power density delivered by the end effector is typically reduced below the threshold of cutting. In some cases (e.g. a monopolar coagulation instrument) a modulated sine wave is used with the overall effect being a slower heating process which causes tissue to coagulate rather than burn and/or char to the point of cutting. In some simple dual function coagulation/cutting devices, a lower duty cycle is used for a coagulation mode and a higher duty cycle is used for a cutting mode with the same equipment. Coagulation and in particular vessel sealing techniques present unique challenges in electrosurgery
While some modern electrosurgical generators provide modulated waveforms with power adjusted in real time based on changes of the tissue characteristics (e.g. impedance), none have been able to address the complexities and sensitivities that arise when dealing with blood vessels located in delicate surgical sites or other difficult to reach blood vessels. None of the prior art or products currently offered combine aspects of applied pressure, low-power energy delivery, waveform modulation, and instrument size/configuration to safely and effectively seal the blood vessels that are often presented in micro-surgical procedures, difficult to access anatomy or pediatric general surgery.
Recent advances in vessel sealing technology have specifically abandoned an attempt to address this specialized market and instead focus on larger devices and techniques for sealing larger vessels more commonly found in general surgery or on “one-size-fits all” devices. U.S. Pat. No. 5,827,271 describes how earlier attempts to seal vessels with electrosurgery were unsuccessful in part because they attempted to apply relatively low currents to the vessels. As a solution, the advances described in U.S. Pat. No. 5,827,271 relate to increasing the current applied to the blood vessel above a certain threshold. The prior art in this field is consistent in its recognition that a high current and high generator power output is required to seal vessels. None of the prior art addresses the unique circumstances presented with small caliber blood vessels that present during micro-surgical procedures, difficult to access anatomy or general surgery in pediatric patients. None of the art accounts for a technique or device that effectively and safely seals blood vessels with an instrument that is smaller in size (both in the shaft and entry point features) and configured to be more effective which working in smaller spaces and with smaller vessel calibers. None of the prior art recognizes the role of the surgical instrument size and end effector surface area in the development of effective vessel sealing techniques and energy delivery sequencing.